American mercenary flyers in the service of France bombarded Chefchaouen. Outcome For the final attack commencing on 8 May 1925, the French and Spanish had ranged 123,000 men, supported by 150 aircraft, against 12,000 Rifians. Superior manpower and technology soon resolved the course of the war in favour of France and Spain. The French troops pushed through from the south while the Spanish fleet and army secured Alhucemas Bay by a landing operation in September (the first amphibious landing in history where tanks and seaborne air support were used) and began attacking from the north. After one year of bitter resistance, Abd el-Krim, the leader of both the tribes, surrendered to French authorities, and in 1926 Spanish Morocco was finally retaken. However, the unpopularity of the war in Spain and the earlier defeats of the Spanish military contributed to the instability of the Spanish government and the military coup of 1923. Atrocities Spanish atrocities and use of chemical weapons Beginning in 1924, the Spanish used chemical weapons during the conflict, which marked the first widespread employment of gas warfare in the post-WWI era. The Spanish army indiscriminately used phosgene, diphosgene, chloropicrin and mustard gas also against civilian populations, markets and rivers. Spain signed the Geneva Protocol in 1925, that prohibited the use of chemical and biological weapons in international conflicts, while simultaneously employing these weapons across the Mediterranean. Some have cited the Spanish chemical weapons as the main reason for a widespread Cancer occurrence in the Rif region, which is still the highest in Morocco; for example, according to the Head of the Association of Toxic Gas Victims (ATGV) research has shown "there are strong indicators that the cancer is caused by the gases that were used against the resistance in the north." Writer Juan Pando, however, pointed out that areas of France and Belgium, which were gassed far more heavily during World War I, do not have abnormal cancer rates. Miguel Alonso, Alan Kramer and Javier Rodrigo wrote in the book Fascist Warfare, 1922–1945: Aggression, Occupation, Annihilation: "Although the Rif War was no 'fascist' war, several methods used to 'pacify' the population were applied in the post-colonial of godless Republican Spain … Apart from deciding not to use chemical weapons, Franco's campaign to 'cleanse Spain' resembled that in Morocco: intelligence-gathering through torture, summary executions, forced labour, rape, and the sadistic killing of military prisoners." Spanish mutilations of captured Moroccans